Document skip-quality-gate directive and refine pre-validation in AGENTS.md#

Problem#

Two shipped behaviors — the skip-quality-gate directive and the refine pre-validation — were live but undocumented, creating a gap for agents and contributors who need to understand how and when to use them.

Task / Link#

Closes #249

Changes#

• Added ### skip-quality-gate Directive subsection to the Directive System section documenting purpose, usage, one-time consumption behavior, and guardrails (deliver phase only, does not skip code review)
• Added ### refine Directive — Pre-Validation subsection documenting eligibility (status=gated), rejection behavior for terminal and non-gated states, and concrete remediation steps
• Both subsections include source file references for cross-checking against implementation

Notes#

No code changes — documentation only. Content derived directly from directive.service.ts and phase-router.service.ts.

Testing#

Manual review of AGENTS.md to confirm accuracy against implementation.